Railway signaling



Jan. 31, 1928. 1,657,468

L. O. GRONDAHL RAILWAY SIGNALING Filed April 16, 1921 Z Sheets-Sheet l R1 INVENTOR.

jag-W 5 44b ,1 'I'TORNEY.

Jan. 31, 1928.

L. O. GRONDAHL RAILWAY smmuue Filed April 16. 1921 .4 TTORNE Y.

I N VENTOR.

2 Sheets-Sheet 2 Patented Jan. 31, 1928.

(UNITED STATES PATENT OFFICE.

LABS GRONDAHL, OF PITTSBURGH, PENNSYLVANIA, ASSIGNUR TO THE UNION SVVITGH &; SIGlil'AL COMI'ANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

RAILWAY SIGNALING.

Application filed April 16, 1921. Serial No. 461,783.

My invention relates to railway signaling, and is particularly well adapted to signaling of the type wherein roadside signals are governed by track circuits which in turn I; are controlled by the passage of cars or trains along the track. a

I will describe several forms of signaling apparatus embodying my invention, and will then point out the novel features thereof in the claim.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one form of apparatus embodying my invention. Fig. 2 is a view showing a modification of the arrangement of the apparatus shown in Fig. 1. Fig. 3 is a diagrammatic view similar to Fig. 1, but showing a modified form of apparatus also embodying my invention. Fig. 4: is a view showing a rearrangement of portions of the apparatus shown in Fig. 3

and embodying my invention.

' Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the reference characters F and F designate the track rails ofa railway along which tratlic normally moves in the direction indicated by the arrow. These rails are divided into a plurality of successive track sections AB,

BO, C-D, etc, the isolation of the track sections being accomplished, as'here shown, byinsulated joints 2 in both of the lines of rails. Any other suitable method of isolating the sections may be employed, however,

without departingfrom the spirit and scope of my invention.

Located adjacent the entrance end of each track section is a signal designated by the reference character S, with an exponent cor- 4Q responding to the location. Each signal, as here shown, comprises three lamps G, Y and R, arranged when lighted to indicate proceet, caution and stop, respectively.

Connected across the rails of each track section adjacent the exit end thereof is a suitable source of track circuit current, which, as here shown, is the secondary 3 of a transformer designated T with an exponent corresponding to the location. The

primary 4 of each transformer T is connected with a transmission line 5, which is constantly supplied with alternating signaling current by a generator 6. Adjacent section. It will be seen, therefore, that each track section is provided with a track circuit comprising the rails of the sectlon, a source of current at the exit end of the section and four heating units connected in multiple across the rails at the entrance end of the section.

Associated with each heating unit is an element designated E with a suitable exponent, which element is responsive to variations in temperature by varying in electrical resistance. Each element E is so located as to receive heat from the associated heating unit H, and for this purpose the materials constituting the heating unit and the .element will usually be in close proximity. Each element E is preferably made of a material having a large temperature co-eflicient, that is, a material which responds to a given change of temperature by a comparatively large change of electrical resistance. These elements may be, for example, Nernst filaments, copper oxides, or various other materials having similar properties. Each element E has a positive temperature co-eliicient, that is, its electrical resistance increases with increase of temperature. Each of theremaining elements E and E has a negative temperature co-eificient; that is, its electrical resistance decreases with increase of temperature. acteristics of the several elements are indicated on the drawing by the symbols and adjacent the elements. In practice it may be found of advantage to place transformers in the circuits between the elements E and the lamps. The elements E control the signals S in the manner which I will now explain.

Referring specifically to signal S Fig. 1, the stop lamp R is provided with a circuit which is supplied with energy from a secondary 12 on transformer T and which ineludes the positive coefficient element E. This circuit is from secondary 12, through wires 7, 8 and 9, stop lamp R, element E, and wire 10 to secondary 12. The parts of this circuit are so adjusted that when track section BC is unoccupied, that is, when element E is heated, the resistance of the These charcircuit is such that lamp R is extinguished.

transformer T through wire 16', negative "When the track section BG is occupied, however, the supply of current to the heating unitH is diminished, so'that element .12 cools and the consequent decrease in reand 1l,SU.Cl1 stop lamp being controlled in.

the same manner as lamp R for signal S.

It follows, therefore, thatwhen track section A-B is unoccupied, lamp Y of signal S will be extinguished, but that when section rt -B occupied by a car or train, the How of currentin lamp Y of sigmal'ti increases to' such value that this lamp becomes lighted. The circuit of lamp Y incluees the negative co-efii cient element E which is controlled by the heating unit H of section B-C. hen section BC is unoccupied, the resistance of element E is so low that it does not interfere .with the control. of lamp 'Y by the'element E. at location B. If, however,.a trainenters section BC while section Al3 is occupied, the resistance of element E increases to such value as to pre vent lamp Y from becoming lighted.

Lamp G for signal S 18 provided wlth a cireu1t which passes from a secondary 15 of co efficient element E wire 17, negative coefficient element E wires 18, 8 and 18, and lamp G to the secondary 15 of transformer T9. The parts of this circuit are so adjusted that when both elements E and-E are heated, sufic-ie nt current flows in the circuit B-G are unoccupied.

to light lamp G. This condition exists, of course, only when both'sections A B and If either of these sections is occupied by a train, one or the other of theelements E or E will become cooled and the resistance of such element.

will then be sufficient to" reduce the current inthe circuit of lamp Gbelowthe point of luminosity; The same result is attained, of

p course, when both of these sections are occu' duced in the circuit of this lamp by element,

E 1 Lamp Y of this signal is extinguished because. of the lngh resistance of GlGT'lQl'llZ E Lamp R has become illuminated, however,

because of the low resistance of element E",

'sothat signal S indicates stop. in signal S lamp G is extinguished, because of the high resistance of. element E atlocation l3, and lamp Riis extinguished because of the high resistance of the element 'E at location C. Lamp Y is lighted, however, because lamp R of signal S is lighted, and so it follows that signal S indicates caution.

for signal S lamp ll is extinguished because of the high resistance of element E at location D, and lamp Y is extinguished because of the high resistance of element E at location C. Lamp G is lighted, however, because both of the elements it and E in circuit with this lamp are of low resistance, and so signal S indicates proceed.

Referring now to Fig. 2, .l have here shown a modification of the apparatus shown in Fig. 'l by virtue of which the amount of energy abstracted from the track circuit is materially reduced. The four heating units which are connected with each track circuit in Fig. l are replaced by a single heating unit H in Fig. 2, which unit controls the resistance of a negative co-cllicicnt clcu'ient E. This element in turn controls the heating units H", H, ll and H through a circuit. which passes (see location C) from secondary. 12 of transformer T through wire 19, heating: unit H, wire 20, heating unit H, wire 21, heating unit H, element. E, wire 22, heating; unit l-l'* and wire 10 to the right-hand terminal of secondary 12. It will be seen, therefore, that when the track circuit is unoccupied, each of the heating units is supplied with current, but that when the track circuit becomes occupied, the resistance of the heating unit circuit is materially increased. due to the influence of the negative co-cliicient element .l. and the units H, H", H and @l-li are then coo ed. The heating units H" to H control temperature responsive elements IE to E inclusive, in the same manner as in Fig. l, and the control of the signals 8 by the elements E is exactly the same as in Fig. l. The structure and operation of Fig. 2 will be apparent, therefore, without further discussion.

It will be seen that with the arrangement of apparatus shown in Fin. 2, onl a small amount of com'rollinp enegy need be taken from the track circuit, and that the energy employed for actually heating the units H to H inclusive, is taken from the transformer secondary 19.. As in 1, transformers may be introduced between the elements E and the lamps.

Referring now to Fig. 3. the three lamps R, Y and of each s gnal are connected in multiple across the terminals of a secondary 34. of the adjacent transformer T. Included in the branch for the lamp R is an element E having a positive temperature co-cificient.

Included in the branch for lamp Y an element E having a. negative temperature co efficientand an element E having a positive temperatme co-cllicient. The branch for lamp (-7: includes two elements E and E, each having a negative temperature co-ctli cient. Each element E is provided with u former T heating unit designated IT with a suitable exponent. As in. Figs. 1 and 2, the heat responsive elements may be used to control the current in the primary of a transformer the secondary of which supplies the current to the lamps.

Each track section is provided with a track circuit comprising transformer secondary 3, and a heating unit designated H with an exponent corresponding to the loca tion. Each heating unitH controls a negative temperature co-eilicient element desig nated E with an exponent corresponding to the Location. This element E controls certain of the heating units for the signal at the same location, and also certain of the heating units for the next signal in the rear. Considering element E for example, the circuit for this element passes. from secondary 34 of transformer T through wire 24, heating unit H, wire 23, unit H wire 25, unit H wire 26, element E wire 27, unit H at location G, wire 28, unit H at location 0, and wires 29 and 32 to secondary 34 of trans- It will be seen, therefore, that when track section AB is unoccupied, heat is supplied to the elements E, E and E at location B, and also to the elements E and at location C.

Referring specifically to signal S, the circuit for stop lamp R is so adjusted that this lamp is extinguished when unit H is heated; that is, whensection BG is unoccupied, and is lighted when unit H is cold; that is, when section 13-0 is occupied. The lamp Y is controlled by element E, which is governed by section BC, and is further controlled by element E which is governed by section AB. Assuming that section BC is unoccupied, so that the resistance of element E is low, this lamp is extinguished when element E is hot, that is, when section AB is unoccupied, but is lighted when element E is cold, that is, when section A--B is occupied. If section B-C becomes occupied while section AB is occupied,

I however, the consequent cooling of element E will extinguish lamp Y. Lamp G is controlled by negative co-eiiicient elements E and E the former of which responds to section PC and the latter to section A-B. In order to light lamp Gr both of these elements must be hot, that is, both of these track sections must be unoccupied; the cooling of either element due to occupancy of the corresponding section serves to extinguish the lamp.

As shown in the drawing, section A-B is occupied by a car or train Lamp Gr of signal S is extinguished due to the cooling of element E and lamp Y is extin guished due to the cooling of element E Lamp R is lighted, however, due to the cooling of element E, and so signal S indicates stop. Considering signal s lamp G is extinguished ,due to the cooling of element E and lamp R is extinguished because element A is hot. Lamp Y is lighted, however, dueto the cooling of element E so that signal S indicates caution. As for signal S the proceed lamp G is illuminated because both elements E and E are hot. The caution lamp Y is extinguished because both elements E andE are hot, and the stop lamp R is extinguished because element E is hot. Signal S therefore, indicates proceed.

Referring now to Fig. 4, the system shown therein is a modification of the system of Fig. 3 in that the heating units at each signal location are controlled by two master units, one of which responds to the condition of the adjacent track section and the other to the condition of the track section next in advance. Each track section is provided as in Fig. 3 with a unit designated H with a letter exponent corresponding to the location. Considering location B, for example, the track circuit for section AB includes a heating unit H which controls a negative co-efiicient heat responsive element E This element E governs a master heating unit H at location B, and another master heating unit I-I at location C. The circuit for these heating units passing from secondary 34 of transformer T through wire 32, heating unit H element E wire 40, heating unit H and wires 41 and 24 to the secondary 34 of transformer T It will be seen, therefore, that when track section AB is unoccupied, each of the master units H and 11% is heated, but that each of these units becomes cool when section A.B is occupied by a car or train. As in Fig. 3, transformers may be added between the elements E and the lamps.

Referring specifically to signal S", the three heating units H, H and H are governed by the master element E the circuit being from secondary 34 of transformer T through wire 24, unit H, wire 39, unit H wire 38, unit H element E wire 37, and wire 32 to secondary 34. The heating units H and H on the other hand, are controlled by the master element E the circuit being from secondary 34 of transformer T through wires 24 and 36, unit H wire 35, unit H master element E and wire 32 to secondary 34. It will be seen, therefore, that the supply of current to the units H to H inclusive, is responsive to the presence and absence of trains in exactly the same manner has with the apparatus shown in Fig. 3. The operation of the apparatus shown in Fig. 4

will be apparent, therefore, without further explanation.

Although I have herein shown and described only four forms of apparatus enibodying my invention, it is understood that various changes and modifications may be spirit and scope of my invention.

Having thus described my invention what Incom-bination, two successive sections of element exposed to heat from said unit, two

' master heating units one for each section and made therein within; the scope of the zip pended claim Without departing from the i emme both controlled by said element, a master temperature-1'esponsive element for each master unit, a group of secondary heating units for each section controlled by the mas t-er' element for the section, a secondary temperature-1esponsive element for each secondary unit, and signals for the sections controlled by said secondary elementsm In testimony whereof I aflix my signature.

LARS o. GRONDAI-IL. 

